Quality Rivets for CNC Machining(3d printing prototyping Angelo)
- source:WEINBERG CNC Machining
What are Rivets?
A rivet is a mechanical fastener that connects two or more materials by inserting a metal shaft through aligned holes in the parts to be joined. The rivet shaft has a head on one end and a tail on the other. During installation, the tail end is deformed, usually with a rivet gun, to create a second head that securely clamps the materials together.
Rivets come in a variety of head shapes, shaft diameters, and materials to accommodate different joining needs. Some common types include blind rivets, solid rivets, drive rivets, and specialty rivets like tubular and split rivets. They are used extensively in manufacturing, construction, aviation, and other industries where high-strength, permanent fastening is required.
Key Properties of Quality Rivets
When selecting rivets for CNC machined parts and assemblies, there are several key properties that indicate higher quality:
- Strength and Ductility - The rivet must be strong enough to handle expected loads without failing. Ductile materials like steel, aluminum, and copper alloys are preferable to brittle ones. The rivet should deform during installation but not break.
- Dimensional Consistency - Dimensional variation in the shaft diameter, head height, and other features should be minimized. This allows for smooth, repeatable insertion into properly sized holes.
- Materials Compatibility - The rivet material should be compatible with the materials being joined to avoid galvanic corrosion. Using the same or similar alloys is ideal.
- Tight Dimensional Tolerances - The shaft diameter, head diameter, and length should meet tight tolerances to ensure consistent fit and optimal clamping force.
- Smooth Surface Finish - The surface should be free of burrs, pits, and other defects to allow easy insertion and good contact between parts.
- High Shear and Tensile Strength - The rivet must maintain clamping force under expected loads without cracking or being pulled out. Harder alloys generally have higher strength.
- Consistent Mechanical Properties - The hardness, yield point, ultimate tensile strength, and other properties should have minimal batch-to-batch variation.
Why Rivet Quality Matters in CNC machining
In CNC machining, poor quality rivets can undermine the performance of the finished product and complicate assembly. Here are some of the issues that may arise:
- Poor Hole Alignment - Inconsistent rivet dimensions lead to loose or overly tight fits, causing misalignment of holes during assembly.
- Variable Clamping Force - Differences in rivet strength or ductility produce unequal clamping force between joints, resulting in weaknesses.
- Insertion Issues - Defects like surface irregularities and diameter variations cause problems inserting rivets smoothly. This damages parts and slows production.
- Early Failure - Weak or brittle rivets are more prone to cracking, shearing, pull-out, and other modes of premature failure under working loads.
- Corrosion - Dissimilar metals or impurities in the rivets can lead to galvanic corrosion at joints, compromising strength and aesthetics over time.
- Re-work and Rejects - Bad rivets must be drilled out and replaced, wasting time and materials. In severe cases, the parts must be scrapped entirely.
In short, inconsistent or poor quality rivets undermine the engineering intent of CNC machined products while driving up manufacturing costs.
Sourcing High Quality Rivets
When sourcing rivets for CNC work, quality should be the top priority. Here are some recommendations:
- Purchase from established manufacturers with a reputation for quality. Look for tight process controls and rigorous testing.
- Review supplier data sheets for details on dimensions, mechanical properties, surface finish, and tolerances. Confirm they meet specifications.
- Request samples and perform quality assurance checks, measuring key parameters and testing performance.
- For custom rivets, work with the supplier to define the required specifications and capabilities.
- Ask about quality control procedures like sampling rates, inspection methods, and batch traceability.
- Make sure the supplier provides Certificates of Conformance and test reports for each shipment.
- Start with small orders or trial batches to validate quality before committing to large volumes.
- Perform periodic audits of the supplier’s processes, or have them assessed by a third party.
Investing in high quality rivets from reputable sources is a wise move for CNC shops. The upfront cost is minor compared to the headaches and delays created by using subpar rivets. With good planning and diligence, manufacturers can obtain ideal rivets to optimize their machining operations. CNC Milling